That could happen, but most companies probably use the same terrible interview for everyone but their friends, which, while unethical, is lawful.
Wait, why is it unethical? It's frustrating and inconvenient and sucks for everyone but their friends. But, unethical? On what grounds? I don't have an obligation to give strangers the same favors I give my friends, do I?
You have an obligation not to waste people's time, especially if you are putting up the facade that they might actually be in the running. The modern interview process can take weeks or even months to get through. If you're just going to hire your friends, can you give the other candidates those weeks or months of their lives back?
The whole premise of interviewing and opening to the pool of candidates is to evaluate and give every applicant a fair chance after passing a minimum bar. If the whole point was to favor or employ someone (pre-decided or friend), then why this facade?
If you have a preferred candidate for a role and that candidate isn't being vetted by exactly the same process as the rest of the candidates, you're obligated to disclosure something to that effect. You might not come right out and say "you should know, we have a preferred candidate", but you need to say something.
Wait, why is it unethical? It's frustrating and inconvenient and sucks for everyone but their friends. But, unethical? On what grounds? I don't have an obligation to give strangers the same favors I give my friends, do I?